Regulated current supply apparatus



D. E. TRUCKSESS Filed June 11, 1949 INVENTOR ATTORNEY a WV a 04m)[UM/P70001555 Nov. 6, 1951 REGULATED CURRENT SUPPLY APPARATUS PatentedNov. 6, 1951 REGULATED CURRENT SUPPLY APPARATUS David E. Trucksess,Summit, N. 1., asaixnor to Bell Telephone Laboratories,

Incorporated,

New York, N. Y., a corporation of New York Application June 11, 1949,Serial No. 98,804 Claims. (01. 321-22) This invention relates to powersupply apparatus, and more particularlygto certain improvements incurrent regulated power supplies. The invention is particularlyapplicable for the rectification of alternating current, providing aclosely regulated constant current output.

Throughout the description of the invention, reference will be madegenerally to rectifiers; it is to be understood that such rectifiers maybe of the metallic disc type, employing semiconductive materials such asselenium or copper oxide, or may be of the thermionic discharge orvacuum tube type. In either case, either half or full wave rectificationmay be employed. Other types and systems of rectifiers may be employedin accordance with the invention "without departing from the spirit andscope thereof.

With reference to communications apparatus, it is often desirable toemploy a direct-current power supply wherein the output current ismaintained at an amount constant within certain defined limits. Toobtain such constant current output, the use of a thermionic dischargetube having its electron path in series with the output oi the rectifierhas been shown, for example, in United States Patent No. 2,075,966 to A.W. Vance, granted April 6, 1937. Means are employed responsive to theoutput current to mode ulate the electron flow in the thermionic discharge tube, thus varying the resistance resultant from-the plateresistance or the discharge tube and maintaining the current at aconstant value within the limits of tube operation. When wide variationsof plate resistance are required of a series-regulating discharge tubearrangement, operation becomes less satisfactory because of the limitedoperating range of the discharge tube employed.

According to one mode of the invention, seriesregulator "thermionicdischarge tubes are emplayed in series with the output of a rectifier.

The operation oi the series-regulator tube is maintained at its optimumoperating point by varying the alternating voltage impressed upon therectifier in response to the voltage drop existent across theseries-regulator tubes. The alternating voltage is varied by means of aservo system including a motor-driven, continuously tapped transformer;the energization of the servomotor is controlled by apparatus responsiveto the voltage drop across the series-regulator tubes. The main objectof this invention is' to provide a rectifier having a substantiallyconstant current output over a wide range 01' al plied loads, unlimitedby the margins of operation oi the series-regulator discharge tubes. 7

The invention is described in detail in the following specification:

Fig. l, the sole figure, shows a schematic diagram of a circuit inaccordance with a preierred embodiment of the invention.

Referring now to the figure, a source of alternating-current supply isapplied to terminals 1 and 2. This alternating current is supplied to anautotransiormer 3, having a variable tap 3-a; the output of theautotransiormer is between terminal I of the alternating-current supplyand variable tap 3-a. Voltages between zero and the 1 line voltagebetween terminals 1 and 2 may be obtained by adjusting the variable tapalong the winding of the autotransiormer. The output of autotransformer3 is supplied to the primary of a transformer i.

Transformer t and bridge rectifier 5 comprise the main rectifier system;the transformer 4 is used to elevate or depress the line voltage supply,providing a rectifier output voltage having a value as may be requiredby the load. Transformer i may be dispensed with if the requiredrectifier output voltage is in the region of the voltage of thealternating supply. Rectifier 5 is shown as a metallic disc bridgerectifier, but as previously stated, many types of rectifiers may beused. A smoothing filter, comprising induct ance B-a and capacitance8-12, is employed to aid in eliminating the output ripple resulting fromthe rectification of the alternating current. One output lead "I of therectifier is supplied directly to a load H; the remaining output lead 8is supplied to the anodes of thermionic discharge tubes 9 and iii.

Thermionic discharge tubes 8 and in are the series regulator tubes andtheir function is substantially similar to that of a comparable tubeshown in the United States Patent No. 2,075,966 to A. W. Vancepreviously alluded to. While two tubes 9 and I0 are shown, any number oftubes may be employed depending upon the relative load current and tubecapacity. The anode-cathode resistance of the series-regulator tubeswill be varied in a manner responsive to the load current; by varyingthis anode-cathode resistance, the load current may be maintainedconstant within the marginal limits of seriesregulator tube operation.To provide the variable resistance operation heretofore mentioned, thepolarity of the voltage supplied to the anodes of the tubes on lead 8must be positive with respect to the cathodes of tubes 9 and Hi. Thislatter requirement means that for the circuit shown, the lead'u musthave a positive potential with respect to lead l. However, the situationof the anode-cathode circuit with regard to the output leads or therectifier S is not material to the invention as long as the anodes ofthe series-regulator tubes 9 and III are maintained at a more positivevoltage than the cathodes.

In the circuit shown, the current passes from the cathode of theseries-regulator tube through resistive elements LI and I2, and throughthe windings of a polarized relay I3 to the load 41. The voltage dropoccurring across resistive element l2 and the winding 01' the polarizedrelay l3 will depend upon the load current. 4

A thermionic discharge tube II is employed as a direct coupledamplifier. e control gridcathode circuit of tube I4 is conn ted in aseries circuit with resistance II; the winding of polarized relay l3; aresistive element l5; and a portion of the resistance of potentiometerI, depending upon the position of the arm oi this potentiometer. supply48 is shown, providing a direct-current voltage between point I! and thejunction of resistances l8 and I9, a. battery or other suitable means ofproviding direct-current potential may be utilized. In any event, thejunction of resistances l8 and I9 is provided with a positive voltagewith respect to point I1; a current will fiow from the cathode to theanode of amplifier tube It in accordance with the potential of itscontrol grid-cathode circuit.

The potentiometer It will be at a potential positive with respect topoint I! because of the positive voltage applied from the output 01'rectifier 48 through resistance 29 and 2| to the potentiometer l8.Alone, therefore, the resistance l5 and potentiometer 16 would provide anegative bias to the control grid of the amplifier tube I I. Theresistance l2 and the polarized relay 13 will develop a voltage dropdependent upon the magnitude of the load current as previously shown andthis voltage will be applied to the control grid-cathode circuit ofamplifier tube it, added with the negative bias developed by H and I8.Recalling the polarity of the rectifier with regard to the flow ofoutput current, it will be seen that a voltage opposed to the negativebias voltage or potentiometer l6 and resistance IE will be developed;increasing load current will make this opposing voltage larger inmagnitude. Assuming that the load current has an optimum value at somegiven point, the voltage across it and I3 resultant from such an optimumfiow oi current can be-made to have a given magnitude relative to theopposing negative bias voltage ofiered by resistance l5 andpotentiometer l5, by adjustment of the tap oi potentiometer 16. As aresult, the operating point of amplifier tube it may be adjusted at theoptimum load current condition.

The anode of the amplifier tube is direct coupled to the control grid ofthe series-regulator tubes 9 and ID. The cathodes oi the seriesregulatortubes 9 and I0 are operated at a potential sufllciently high to providethe properrelationship between their control grids and the anode ofamplifier tube H. The auxiliary rectifier system 48 has that portion orits voltage output from resistor 20 to point maintained at a virtuallyconstant level through the use of a gaseous discharge regulator tube 23.This will maintain the bias voltage for amplifier tube l4 andseries-regulator tubes 9 and ID at substantially constant values.

Assuming for the sake of illustration that the Although an auxiliaryrectifier' the optimum, the magnitude of the voltage drop acrossresistance 82 and polarized relay I 3 will increase and the control gridof the amplifier tube It will become relatively more positive, or lessnegative. The increased positive control rid voltage will cause anincreased fiow of anode current in the amplifier tube. This increasedanode current fiow will provide a larger drop of voltage acrossresistance 22 and the point of the junction of resistances l8 and [9will be depressed in voltage. In turn, this depressed voltage issupplied through resistance H to the control grid 01' theseries-regulator tubes 9 and 10. By a suitable choice for the value ofresistance Hand of the other circuit constants, the seriesregulatortubes 9 and it) may be adjusted to have a given anode-cathode resistanceat the optimum given value of load current. The more negative voltage atthe control grids of series-regulator tubes 9 and I 0 will, in turn,modulate the electron flow from the cathode to anode of .theseriesregulator tubes to restrict current fiow. Such a restrictedcurrent flow will act as a resistance in series with the output lead 8of the rectifier 5, reducing the voltage supplied to the load andtending to return the rectifier load current to the optimum value.Similarly, it can be shown that an assumed decrease in load current fromoptimum will cause a decrease of resistance of the series-regulatortubes 9 and I0, tending to restore the output current to the optimumamount.

As stated in the summary of the invention, the use of series-regulatortubes such as 9 and ill to control the magnitude of the load current isrendered difiicult over wide ranges of load, as the series-regulatortubes approach limits of operation. In order to keep theseries-regulator tubes operating within reasonable limits of operatingmargin, a circuit according to the invention is employed to assist inregulating load current.

A gaseous discharge tube 24 is employed as a reference voltage standard.Resistances 25 and 9 are connected to each other in series and togatherin the paralleled anode-cathode circuits of series-regulator tubes 9 andiii. The gaseous discharge tube 24 is supplied with an operatingpotential from a second auxiliary rectifier 27 through the ballastresistance 28. The voltage between points B and C will be maintained atthe regulated value of the gaseous discharge tube substantiallyindependent of line voltage and component variations. The voltage dropacross resistances 25 and 26, and thus between points A and B will bedetermined, in turn, by the voltage drop across series-regulator tubes 9and iii. It has been shown that the value of resistance developed acrossseries-regulator tubes 9 and i0 depends upon the load current; e. g., asthe load current increases, the resistance ofiered by seriesregulatortubes 9 and It will tend to increase and the voltage drop across theseries-regulator tubes will be increased. Similarly, as the load currentdecreases, the resistance offered by tubes 9 and M will tend todecrease, and the voltage drop across tubes 9 and Ill will be decreased.It may therefore be said that the voltage existing between points A andB will depend ultimately upon the load current when the output voltageof rectifier 5 is constant. By properly proportioning resistances 25 and25, the voltage developed between points A and B can be madesubstantially equal to the voltage across points B and C for loadcurrentfrom the main rectifier 5 rises from that value ofseries-regulator tube voltage drop corresponding to the optimum value ofload cur-- rent.

When series-regulator tubes 3 and II have a voltage drop reflecting theoptimum value of load current, the voltage developed between points Aand B, and B and C being made equal and 0D- posite, the voltage betweenA and C will be zero. Optimum conditions of load current may well referto the mid-point of operation of the seriesregulator tubes. Assuming anincrease in the load current, the voltage between A and B will increasecorrespondingly, but the voltage between B and C will remain constant.Thus, the sum of these two voltages at A and C will rise from zero tosome value of given polarity. Conversely, a depression in the voltagedrop across the seriesregulator tubes 9 and I0, reflecting a decrease inload current, will produce a corresponding decrease in the voltageacross A and B. As the voltage across B and C still remains constant, avoltage of opposite polarity to that resulting,from an increasing loadcurrent will be derived at points A and C. It will be seen that themagnitude of the voltages developed across A and C depends upon themagnitude of the displacement of the voltage drop acrossseries-regulator tubes 9 and ill from the optimum value.

The signals derived at points A and C are supplied to a phase detectorincluding thermionic discharge tubes 29 and 30. A transformer 3|, havingits primary connected to a particular source of alternating current, hasits secondary connected between the anodes of phase detector tubes 23and 30. A center tap of the secondary of transformer 3| is connectedthrough the primary of a transformer 32 to the cathodes of phasedetector tubes 23 and 33. The control grids of the phase detector tubes23 and 33 are returned to their cathodes through resistances 33 and 34;points A and C, previously described, are connected respectively to thecontrol grids of these phase detector tubes. Assuming that the circuitsof the phase detector tubes 23 and 33 are intrabalanced when points Aand C are at the no-voltage condition, no alternating current will bedrawn through the primary of transformer 32. When a voltage is derivedbetween A and 0, one of the phase detector tubes will have a negativegrid-cathode voltage applied thereto and the other phase detector tubewill have a positive grid-cathode voltage applied thereto; the relativepolarity of the depression or elevation of the control grid voltagedepends upon the polarity of the voltage at A and C. As the control gridvoltage of phase detector tubes 25 and 33 changes, the one of the tubeshaving a positive grid-cath ode voltage will draw more current;conversely, the tube having a negative grid-cathode voltage draws lesscurrent. An alternating voltage is applied to the anode circuits ofthese tubes by transformer 3| a resulting pulsating current will bedrawn through the primary of transformer 32 dependent in phase upon thepolarity of the voltage at A and C.

At such times as the currents drawn by the phase detector tubes 29 and30, respectively, are equal, the secondary of transformer 32 will havesubstantially no voltage induced therein. However, a voltage will beinduced in the secondary of transformer 32 at the other conditions ofthe phase detector tubes as described, having a phase dependent uponwhich of the phase detector tubes is more conductive. This voltage canbe called the servocontrol voltage. The phase shift for the two possibleunbalance conditions respectively,

A phase sensitive servosystem is shown employing two thermionicdischarge servotubes 35 and 33. Transformer 31 has its primary conneciedto an alternating-current supply having the same phase as supplied totransformer 3i. The secondary of transformer 31 is coupled through thedirect-current controP'windings of saturable reactors 38 and 39, laterto be described, to the respective anodes of the servotubes 35 and 36.The center tap of the secondary of transformer 31 provides a return pathfrom the anodes to the cathodes of these tubes. The grid-cathodecircuits of tubes 35 and 36 comprise the halves, respectively, of thesecondary of transformer 32. Interposed in the circuits between thesecondary center tap of transformer 32 and the common cathodes of tubes35 and 36, is a bias supply comprising: a rectifier 40. a rheostatill-a. and a transformer 4!, the latter connected to analternating-current supply. While such a rectifler, rheostat andtransformer may be employed to supply the negative bias required forservotubes 35 and 35, other bias means, such as a battery, may beemployed with equal success.

The saturable reactors 38 and 33 have been alluded to. One mode ofconstruction for these reactors comprises the use of two-windings oneach reactor, one being a variable impedance winding and the other adirect-current control" winding. It has been found convenient to employa core of magnetic material having three legs: the outer two legs havingthe variable impedance winding thereon, while the center leg has thedirect-current control winding thereon. By

varying the unidirectional/or direct current passing through the lattercontrol winding, it will be possible to vary the saturation of themagnetic core of the reactor. A change in saturation of the magneticcore reflects as a change of reluctance of the core and ultimately,therefore, as a change in the reactance of the variable impedancewinding. It can be seen that the impedance of the latter winding willvary in accordance with the flow of current through the direct-currentcontrol winding. While one form of construction for the saturablereactor has been described, many modes of construction are applicable tothe circuit of the invention.

Depending upon the phase of the current drawn through the primary oftransformer 32, one only of the servotubes 35 and 35 will draw platecurrent. For example, if the grid-cathode voltage and the anode-cathodevoltage of tube 35 are in phase, tube 35 will draw space current.Similarly, if the voltage across the secondary of transformer 32 isshifted in phase by degrees, the grid-cathode voltage of tube 35 will be180 degrees out of phase with its anode-cathode voltage and thegrid-cathode voltage of tube 38 will be in phase with the anode-cathodevoltage of tube 35. Servotube 36 will then draw space current and tube35 will draw no space current. During the periods of time when theprimary of transformer 32 has substantially no pulsating current flowingthrough it, the bias supply from the auxiliary direct-current rectifiersystem 40, II-a and II will normally bias the servotubes 35 and 33 tominimize the flow of current; only when a current of the proper phase isdrawn through the primary of transformer 32, will the appropriateservotube 35 or 36 draw a current. It can be seen that the relativeimpedances of the impedance winding of reacts-noes 33 and 33 will dependupon the magnitude and phase of current drawn through the primary oitransformer 83. The current drawn through the primary transformer 32 hasbeen shown to depend upon the magnitude and polarity oi the voltage atpoints A and C, which, in turn, depends upon displacement of theseries-regulator tubes 3 and I0 from the voltage drop corresponding tooptimum load current;

A two-phased servomotor 42 has one phase winding 42-a connected betweenthe alternatinging of the saturable reactors 38 and 39 are, in

effect, connected together in series across the altemating-currentsupply terminals l and 2. In

normal periods of quiescence, i. e., when the voltage drop across tubes9 and I0 is at a predetermined value, the variable impedance windings oithe saturable reactors 38 and 39 will have substantially equal values.The junction of the two reactors will, therefore, be located at anelectrical mid-point of the alternating-current supply source. Winding42-h is connected between mid-point tap of the supply reactor 43 and thejunction of the saturable reactors 88 and 38. Thus, at the time that theregulating system is in the quiescent condition, both ends of winding42-11 will be at an electrical mid-point of the alternating-currentsupply line; no current will flow through winding 42-b. Although winding42-a of the motor will remain excited, it alone will not causeservomotor 42 to operate; as long as the junction of saturable reactors38 and 39 provide an electrical mid-point of the alternatingcurrentsupply source, winding 42-b will remain unenergized.

As the voltage across the series-regulator tubes 3 and I0 changes fromthe optimum value, the impedance of the impedance windings oi saturablereactors 38 or 38 will change in accordance with the direction andmagnitude of the displacement irom optimum, in the manner described. Asthe ratio of these impedances varies, the Junction of the two reactors38 and 39 will provide a newelectrical point displaced from theelectrical mid-point of the alternating-current supply. As theelectrical position oi the midpoint of the supply reactor 43 remainsinvariable, a voltage will be developed across the winding 42-h of theservomotor. Winding 42-a is constantly energized, the phase of thiswinding being appropriate to cause servomotor 42 to rotate by properselection of the phasing condenser 49; the current through winding 42-11will be substantially in quadrature with the current drawn throughwinding 42-h.

A mechanical linkage couples the rotatable shaft of motor 42 with thevariable tap 3-11 of autotranstormer 3. The rotation of the servomotordrives the variable tap 3-a to some new position on the winding ofautotransformer 3, thus varying the alternating supply voltage to thetransformer 4 and main rectifier 5. This change in voltage will be suchas to affect the output 01' the main rectifier 5, compensating forwhatever displacement in voltage drop across tubes 9 and I0 from optimumoriginally caused the change in the variable impedance windings ofsaturable reactors 38 and 39. Whenever the position of the variable tap3-41 has moved sufilciently so that the output voltage of the mainrectifier 5 has attained a position returning the voltage drop acrosstubes 9 and ill to optimum, the regulating system will again becomequiescent and the relative impedances of the variable impedance windingof the saturable reactors 38 and 39 again become equal and theservomotor 42 ceases to operate.

It has been assumed that the center tap of supply reactor 43 is at itsmid-point and that the impedance windings or the saturable reactor aresubstantially equal at the quiescent point, but this is not essential.As long as the ratio between the arms of saturable reactors 43 isproportional to the relative quiescent impedance of the saturablereactors 38 and 39, the system will operate in the manner described.Turning now to the protective circuits, as the normal condition ofcircuit operation presumes that the load current will remain at aconstant value, a load current condition having a wide variation fromthe optimum amount denotes a condition which should provide warning.Furthermore, if the load current should continue increasing, a point ofload current output may be reached which will endanger the load 41,series-regulator tubes 8 and I0 and rectifier 5. To provide a warning oralarm device and to protect the series-regulator tubes and rectifierfrom overload, a polarized relay I3 has its winding inserted in serieswith load 41. The armature of relay I 3 will remain clear of bothcontacts during the times that the load current is maintained withinpredetermined limits surrounding the optimum point. Centering of thearmature may be accomplished by suitable spring linkages l3-a and I3-battached thereto. In the event that the load current should exceed themaximum predetermined amount, polarized relay I 3 will draw the armatureover to make with its left-hand contact, thereby operating relay 44. Theoperation oi relay 44 will close the righthand armature and contacts toan alarm circuit which may include audible or other means of warning.The left-hand armature will also close against its associated contact;the control grids of the series-regulator tubes 9 and 10 will then beconnected through resistances l9 and 45 to the junction of resistances Hand I2. The latter junction is at a point considerably more negativethan the cathodes of the series-regulator tubes and will, in effect,place a negative bias on these control grids, reducing or cutting oilthe flow of load current through the series regulator tubes.

In the event that the load current decreases beyond the predeterminedunderload amount, the polarized relay i3 will attract its armature tomake with its right-hand contact. This will cause relay 46 to operate,closing its right-hand armature and contact, thus operating the alarmcircuit. With the underload condition, the problems of series-regulatortube and rectifier overload are not significant.

It is obvious that the scope of the invention is not limited to thespecific embodiment described, and that the invention may be employed inarrangements other than as given by way of exfor providingunidirectional current tov a load circuit comprising, a rectifier forrectifying current from an alternating-current source, and for in partthe current in said load circuit, and means responsive to a portion atleast of the voltage drop across the said variable current conductingmeans for controlling the alternating voltage impressed upon the saidrectifier from the alternating-cura rent source, said last-mentionedmeans comprishaving a rectifier to derive a rectified current outputfrom a source of alternating current comprising, a load circuit havingan optimum value of load current, a space charge path to couple therectified current to the said load circuit, means to vary the'resistanceof the said space charge path in accordance with the magnitude of therectified current supplied to the said load, means to derive aunidirectional control voltage from a portion of the voltage drop acrosssaid space charge path having a polarity and magnitude proportionalrespectively to the direction and magnitude of the displacement of therectified current from the said optimum value or load current, and meansfor controlling the alternatlug voltage supplied to the rectifierresponsive to the polarity and magnitude of the said unidirectionalcontrol voltage.

3. In combination, a space current device having a space current path, arectifier for rectifying current from an alternating-current source,means for supplying rectified current from said rectifier through saidspace current path to a load, means responsive to the magnitude of thesaid rectified current for controlling the resistance of said spacecurrent path, a variable reactor, and means responsive to resistancechanges of said space current path for controlling the al- 7 ternatingvoltage impressed on the said rectifier from the saidalternating-current source comprising means coupled across the saidspace current path and energized by current from the said rectifier forcontrolling the reactance of said.

variable reactor, said energization varying in response to resistancechanges of the said space current path.

In a constant current power supply system including a rectifier toderive a rectified current output from an alternating-current supply, aload circuit having an optimum value of load current, the circuitcomprising, a variable resistance space charge path coupling therectified current to the load circuit, said resistance of said spacecharge path lacing responsive to the magnitude of the rectified currentsupplied to the load, means to derive a unidirectional contr l voltagefrom a portion of the voltage drop across said space charge path havinga polarity and magnitude proportional respectively to the direction andmagnitude of the displacement of the rectified current from the optimumvalue of load current, a mechanically variable multiratio transformerinterposed between the rectifier and the alternating-current supp y. anelectric servomotor having its mechanical output coupled to the saidvariable ratio transformer, and polarity sensitive means to energ ze thesaid electric motor in accordance "with the polarity and magnitude ofthe said unioh'ectional control voltage.

5. A system according to claim 4 characterizedinthat the polaritysensitive means comprises a phase detector having first and secondthermionic discharge tubeseach with a cathode, grid and anode. means toapply an alternating voltage of given phase to the anode-cathode circuitor the said first and second thermionic discharge tubes in push-pull,means to couple the said unidirec- 7 tional control voltage to thegrid-cathode circuits of the said first and second thermionic dischargetubes. a regulatory circuit having third and fourth thermionic dischargetubes each with cathode, grid and anode, means to apply the saidalternatin; voltage of given phase to the anode-cathode circuit of thesaid third and fourth thermionic discharge tubes in push-pull, mean tocouple the anode-cathode circuits of the said first and secondthermionic discharge tubes to the grid-cathode circuits of the saidthird and fourth thermionic discharge tubes in push pull, and means toenergize the said electric servomotor in accordance with the ratio ofanode-cathode currents of the said third and fourth thermionicdischargetubes.

6. In a system according to claim 5 characterized in that the means toenergize the said electric servornotor comprises first and secondmagnetically saturable reactors having each an impedance winding and acontrol winding, means to energize the said servomotor through theimpedance windings of the said first and second impendance windings, andmeans to couple the control windings of the said first and secondreactors in the anode-cathode circuits of the said third and fourththermionic discharge tubes respectively.

7. In a. constant current power supply system including a rectifier toderive a rectified current output from a source of alternating current,a load circuit having an optimum value of load current, a space chargepath of variable resistance coupling the rectifier to the load circuit,means to vary the resistance of the space charge path in accordance withthe magnitude of the rectified current supplied to the said load, asource of substantially constant direct voltage, means to derive acomparison voltage from the voltage drop of the said space charge pathand the source of constant direct voltage, said derived comparisonvoltage having a polarity and magnitude proportional respectively to thedirection and magnitude or the displacement oi. the rectified currentfrom the said optimum value of load current, and means for controllingthe alternating voltage supplied to the rectifier responsive to thepolarity and magnitude of the said unidirectional control voltage 8. Ina constant current power supply system including a rectifier to derive arectified current output from an alternating-current supply, a loadcircuit having an optimum value of load current, a space charge path ofvariable resistance ecu pling the rectifier to the load circuit, meansto vary the resistance of the space charge path in accordance with themagnitude of the rectified current supplied to the said load, a. sourceof substantially constant direct voltage, means to derive a comparisonvoltage from the voltage drop of the said space charge path and thesource of constant direct voltage, said derived comparison voltagehaving a. polarity and magnitude proportional respectively .to the senseand magnitude of the displacement of the rectified current from the Isupply, an electric motor having its mechanical output coupled to thesaid variable ratio transformer, and polarity sensitive means toenergize the said electric motor in accordance with the polarity andmagnitude of the said derived comparison voltage.

9. In a power supply system including a rectifier to derive asubstantially constant rectified cur'rentoutput from a source ofalternating current and a load circuit having a given desired loadcurrent value, the combination of a plurality of thermionic dischargetubes each having an anode, a cathode and a grid, means to couple theanode-cathode circuits of the said thermionic discharge tubes in serieswith the rectified current output to the load circuit, means to vary thegridcathode circuit voltage of the said thermionic discharge tube inaccordance with the magnitude of the rectified current supplied to thesaid load, a source of substantially constant voltage, means to derive acomparison voltage from the anodecathode voltage drop of the saidthermionic discharge tubes and the source of constant voltage, saidderived comparison voltage having a vectorial composition proportionalto the vectorial displacement of the rectified current from the givendesired load current value, a variable tap output autotransformercoupling the source of alternating current and the rectifier; anamplifier responsive to the vectorial composition of the said derivedcomparison voltage, and a servosystem energized by the said amplifierand an electric servomotor mechanically linked to the variable tap ofthe said autotransformer, whereby the alternating voltage supplied tothe rectifier is maintained at values providing the given desired loadcurrent.

10. In a power supply system for providing a direct current of optimumconstant magnitude to a load including a rectifier for rectifyingcurrent from an alternating-current source, said rectified current beingsupplied to the load, variable current conducting means responsive tothe said rectified current flowing to the load and means responsive tothe voltage drop of the said variable current conducting means forproviding a control voltage having a vectorial composition in accordancewith the vectorial displacement of the rectified current from theoptimum constant amount, a first and a second thermionic discharge tubeeach having a cathode, grid and anode, mean to energize theanode-cathode circuits of the said thermionic discharge tubes inpush-pull with a given alternating voltage, means to impress the controlvoltage differentially upon the grid-cathode circuits of the said firstand second thermionic discharge tubes, means to derive an alternatingservocontrol voltage from the anode-cathode circuits of the said firstand second thermionic discharge tubes, and means to control thealternating current source supplied to the rectifier in accordance withthe said derived alternating servocontrol voltage.

11. In a power supply system for providing a direct current of optimumconstant magnitude to a load comprising, a rectifier for rectifyingcurrent from an alternating-current source, said rectified current beingsupplied to the load, vari= able current conducting means responsive tothe said rectified current flowing to the load and means responsive tothe voltage drop of the said variable current conducting mean forproviding an alternating servocontrol voltage having a phase andmagnitude dependent upon the polarity and magnitude of the displacementoi t e 12 rectified current from an optimum constant magnitude, a firstand a second thermionic discharge tube each having a cathode, a grid andan anode, means to impress the alternating servocontrol voltage upon thegrid-cathode circuits of the said thermionic discharge tubes, a variabletap autotransformer interposed between the alternatingcurrent source andthe said rectifier, a servomotor linked mechanically to the variable tapof the said autotransformer, and means to energize the said servomotorfrom the anode-cathode circuit of the said first and second thermionicdischarge tubes.

12. In a power supply system according to claim 11, characterized inthat the means to energize the said servomotor comprises first andsecond reactors having each a magnetically saturable core, an impedancewinding and a control winding, means to energize the said servomotorfrom the impedance windings of the said first and second reactors inopposition, and means to couple the control windings of the said firstand second reactors in the anode-cathode circuit of the said first andsecond thermionic discharge tubes.

13. In a power supply system, a space current device having a spacecurrent path, a rectifier for rectifying current from analternating-current source, means for supplying rectified load currentfrom said rectifier through said space current path to a load, meansresponsive to the magnitude of the said rectified load current forcontrolling the resistance of said space current path, means responsivet resistance changes of said space current path for controlling thealternating voltage impressed on the said rectifier from the saidalternating-current source including means coupled in parallel with thesaid space current path and energized by the said load current from thesaid rectifier, said energization varying in response to resistancechanges of the said space current path, and a relay energized by atleast a portion of the said load current at a predetermined maximum ofsaid load current. said relay controlling the said means responsive tothe magnitude of the said rectified current whereby the said rectifiedcurrent is limited to the said predetermined maximum.

14.- In a power supply system according to claim 13, wherein the saidrelay is energized by at least a portion of the said load current at apredetermined minimum f said load current, and a warning indicationdevice activated by the energization of the said relay. J

15. In combination, a rectifier for rectifying current from analternating-current supply source and for supplying rectified current toa load circuit, variable current conducting means I in said loadcircuit, means for decreasing the conductance of said conducting meansin response to an increase of current in said load circuit, and viceversa, and means responsive to a portion at least of the voltage dropacross said variable current conducting means for controlling thealternating voltage impressed upon said rectifier from said supplysource, said last-mentioned means comprising a motor, variable reactancemeans for controlling the energization of said motor, and meansresponsive to said portion at least of the voltage drop across saidvariable current conducting mean for controlling the reactance of saidvariable reactance means.

16. Incombination, a space current device having a space current path, arectifier for rectifying current from an alternating-current supplysource, means for supplying rectified current from said, rectifierthrough said space current path to 13L a load, means responsive to saidrectified current for controlling the resistance of said space currentpath, and means responsive to resistance changes of saiol space currentpath for controlling the alternating voltage impressed upon saidrectifier from said. supply source, said last-mentioned means comprisingmeans having a movable element for changing said alternating voltage, amotor for driving said movable element, variable reacting means forcontrolling the energization of said motor and means responsive to saidres sisiance changes of said space current path for m Number controllingthe reactance of said variable reactance means.

DAVID E. TRUCKSESS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Name Date 2,018,348 Dijksterhuis Oct. 22, 1935

